An investigation of UV disinfection performance under the influence of turbidity & particulates for drinking water applications

Abstract

UV disinfection performance was investigated under the influence of representative particle sources, including wastewater particles from secondary effluent in a wastewater treatment plant, river particles from surface water, floc particles from coagulated surface water, floc particles from coagulated process water in a drinking water treatment plant, and soil particles from runoff water (planned). Low-pressure (LP) and medium-pressure (MP) UV dose-response of spiked indicator bacteria <i>E. coli</i> was determined using a standard collimated beam apparatus with respect to different particle sources. Significant impacts of wastewater suspended solids (3. 13~4. 8 NTU) agree with the past studies on UV inactivation in secondary effluents. An average difference (statistical significance level of 5% or &alpha;=5%) of the log inactivation was 1. 21 for LP dose and 1. 18 for MP dose. In river water, the presence of surface water particles (12. 0~32. 4 NTU) had no influence on UV inactivation at all LP doses. However, when the floc particles were introduced through coagulation and flocculation, an average difference (&alpha;=5%) of the log inactivation was 1. 25 for LP doses and 1. 12 for MP doses in coagulated river water; an average difference (&alpha;=5%) of the log inactivation was 1. 10 for LP doses in coagulated process water. Chlorination was compared in parallel with UV inactivation in terms of particulate impacts. However, even floc-associated <i>E. coli</i> were too sensitive to carry out the chlorination experiment in the laboratory, indicating that chlorine seems more effective than UV irradiation on inactivation of particle-associated microorganisms. In addition, a comprehensive particle analysis supported the experimental results relevant to this study.